Change GpuDataManager to use Observer notifications rather than callbacks

chrome/browser/ui/webui/tracing_ui.cc

Index: chrome/browser/ui/webui/tracing_ui.cc
===================================================================
--- chrome/browser/ui/webui/tracing_ui.cc	(revision 107010)
+++ chrome/browser/ui/webui/tracing_ui.cc	(working copy)
@@ -8,7 +8,6 @@
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
-#include "base/callback_old.h"
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/memory/scoped_ptr.h"
@@ -48,7 +47,8 @@
     : public WebUIMessageHandler,
       public SelectFileDialog::Listener,
       public base::SupportsWeakPtr<TracingMessageHandler>,
-      public TraceSubscriber {
+      public TraceSubscriber,
+      public GpuDataManager::Observer {
  public:
   TracingMessageHandler();
   virtual ~TracingMessageHandler();
@@ -66,6 +66,9 @@
   virtual void OnTraceDataCollected(const std::string& trace_fragment);
   virtual void OnTraceBufferPercentFullReply(float percent_full);
 
+  // GpuDataManager::Observer implementation.
+  virtual void OnGpuInfoUpdate() OVERRIDE;
+
   // Messages.
   void OnTracingControllerInitialized(const ListValue* list);
   void OnBeginTracing(const ListValue* list);
@@ -75,9 +78,6 @@
   void OnSaveTraceFile(const ListValue* list);
 
   // Callbacks.
-  void OnGpuInfoUpdate();
-
-  // Callbacks.
   void LoadTraceFileComplete(std::string* file_contents);
   void SaveTraceFileComplete();
 
@@ -98,9 +98,6 @@
   // Cache the Singleton for efficiency.
   GpuDataManager* gpu_data_manager_;
 
-  // Callback called when the GPU info is updated.
-  Callback0::Type* gpu_info_update_callback_;
-
   DISALLOW_COPY_AND_ASSIGN(TracingMessageHandler);
 };
 
@@ -138,17 +135,13 @@
 
 TracingMessageHandler::TracingMessageHandler()
   : select_trace_file_dialog_type_(SelectFileDialog::SELECT_NONE),
-    trace_enabled_(false),
-    gpu_info_update_callback_(NULL) {
+    trace_enabled_(false) {
   gpu_data_manager_ = GpuDataManager::GetInstance();
   DCHECK(gpu_data_manager_);
 }
 
 TracingMessageHandler::~TracingMessageHandler() {
-  if (gpu_info_update_callback_) {
-    gpu_data_manager_->RemoveGpuInfoUpdateCallback(gpu_info_update_callback_);
-    delete gpu_info_update_callback_;
-  }
+  gpu_data_manager_->RemoveObserver(this);
 
   if (select_trace_file_dialog_)
     select_trace_file_dialog_->ListenerDestroyed();
@@ -190,12 +183,8 @@
     const ListValue* args) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
-  DCHECK(!gpu_info_update_callback_);
-
   // Watch for changes in GPUInfo
-  gpu_info_update_callback_ =
-      NewCallback(this, &TracingMessageHandler::OnGpuInfoUpdate);
-  gpu_data_manager_->AddGpuInfoUpdateCallback(gpu_info_update_callback_);
+  gpu_data_manager_->AddObserver(this);

[Zhenyao Mo, 2011/10/26 00:03:12]

Since we always call RemoveObserver() in destructor, we should move AddObserver
to constructor.

[csilv, 2011/10/26 00:16:14]

This is actually a better approach to do it here.  This way, the callback will
only be invoked after the page is loaded.  If we move this to the constructor,
it may result in the handler trying to execute a javascript function before the
page is ready which yeilds a javascript error.

There's no harm in calling RemoveObserver if it was never added.

 
   // Tell GpuDataManager it should have full GpuInfo. If the
   // Gpu process has not run yet, this will trigger its launch.